implemented sub

WpfTex/LatexEditor/MainWindow.xaml

@@ -10,7 +10,11 @@
         <local:LatexViewer FontSize="80">
 <!--            e^{\pi i}=-1\{\textrm{in the complex plane} \\\\-->
             
-            b^x+b^y=b^{x+y}
+            a^x+a^y=a^{x+y} \\
+            
+            log_ax^n=nlog_ax \\
+            
+            M^1_2
             
 <!--            A \  \alpha \quad N \  \nu \\-->
 <!--            B \  \beta \quad  \Xi \  \xi \\-->

WpfTex/LatexEditor/Parser/Segments/LatexSegment.cs

@@ -76,6 +76,15 @@ namespace LatexEditor.Parser.Segments
                             val.Offset = new Point(val.Offset.X, val.Offset.Y + 0.45);
                         }
                     }
+                    if (head.Value == "_")
+                    {
+                        if (PopLatexSegment(tokens, out var content))
+                        {
+                            val = content;
+                            val.Size *= 0.7;
+                            val.Offset = new Point(val.Offset.X, val.Offset.Y - 0.45);
+                        }
+                    }
                     break;
 
                 case "escape":